head and body length of the single species O. zibethicus
is 229-325 mm, tail length is about 180-295 mm, and adult weight
is 681-1,861 g. The coloration of the upper parts of the pelage
are dominated by the long, shiny guard hairs which provide a
protective layer over the soft dense underfur. The primary color
ranges from medium silvery brown to dark brown to almost black.
The underparts are generally lighter and the feet and nearly
hairless tail are dark brown to black.
zibethicus is particularly well suited to swimming. The
hind foot is partially webbed with a row of short stiff hairs
along its edge which is known as the swimming fringe. In addition
to being almost hairless, the tail is scaly and flattened and
serves as a rudder. The name Muskrat derives the musky odor
secreted from the musk glands in the animal's perineal area.
In males, these glands are larger and open within the foreskin
of the penis. During urination, the secretions mix and are deposited
along the muskrat's route. Females usually have two pair of
mammae; one inguinal pair and one pectoral.
prefer aquatic habitats and can be found in fresh and saltwater
marshes, lakes, ponds, rivers and sloughs. The depth of the
water should be enough to keep it from freezing completely in
the winter, but shallow enough to support a sufficient amount
of vegetation which is not submerged.
threatened, O. zibethicus can remain underwater for as
long as 17 minutes. Average submersions are 2-3 minutes. Largely
nocturnal and crepuscular, the Muskrat may be seen foraging
during the day, especially in winter. Depending on its chosen
habitat, the Muskrat builds one of two types of shelter. Along
flowing streams or canals, a burrow is dug in the adjacent bank
or dike. The entrance is located below the lowest depth of where
the water freezes, and a tunnel extends for as long as 10 meters
to a dry chamber above the high water level. Several burrows
may be interconnected.
marsh or swamp habitats, a mounded house of vegetation such
as cattails and grasses, is built and covered with mud, sheltering
an interior dry nest. The house is built on a clump of vegetation
or directly in the ground and may have tunnels which exit underwater.
The structure is about 1-2 meters wide and 1 meter tall. In
northern climates, O. zibethicus may build a dome of
vegetation over the ice where When the animal can surface through
a hole in the ice to eat.
most valued foods are cattails and bulrushes in North America
and water lilies in Europe. The diet may also include other
vegetable matter and animals such as crayfish, crabs, mussels,
and small fish.
mated pair appears to be monogamous, though the male will live
in a separate nest while the female is suckling her young. The
offspring stay with their parents, helping to maintain the nest,
until they reach sexual maturity. Females are polyestrous. In
the northern part of its range, O. zibethicus usually
has 2 litters per year, while in the south the breeding season
is continuous, producing as many as 5 or 6 litters per year.
Gestation last 25-30 days and litter size ranges from 1-11 young.
Average litter sizes may be as low as 2.4 in some southern areas
and as high as 7.1 in northern areas. Sexual maturity differs
according to geography as well, and is achieved much earlier
in southern areas.
zibethicus is found in North America, north to the treeline,
including Newfoundland; south to the Gulf of Mexico, Rio Grande
and lower Colorado River valleys. Intorduced to Czech Republic
and now widespreaad in the Palearctic, including C and N Europe,
most of the Ukraine and Russia, and Siberia, and adjacent parts
of Mongolia and scattered throughout China, NE Korea, and Honshu
Isl, Japan; also into southernmost Argentina.